Just before the Halloween holidays, a blood moon will occur in the sky just after midnight on Oct. 8, treating stargazers to a crimson view caused by a rare phenomenon.

The second “blood moon” of the year, this year’s red moon will be best viewed from areas close to the Pacific Ocean- if the weather holds out.

Wednesday’s event is the second of four total lunar eclipses that occur in a phenomenon known as a “tetrad.” The last one occurred on April 15 of this year.

Total lunar eclipses happen when a full moon moves straight into the shadow of Earth, causing the moon’s normally bland, pale face to emit a spooky reddish glow. The glow begins with an amber shade, then gradually turns crimson as it moves into the darkest areas of Earth’s shadow.

The moon produces no light and receives illumination from the sun, so the blood-red color is caused by light refracted from Earth’s atmosphere. Factors such as humidity or volcanic activity can affect the moon’s perceived coloring, changing the shade from a pinkish hue to a dark scarlet.

For stargazers along the Pacific Ocean, the penumbral phase will begin at 2:16 a.m., when the moon begins to move into place. Gradually, as the moon moves completely into Earth’s shadow, the crimson hue will appear most saturated between 4:25-5:24 a.m. The eclipse will finally end at 7:34 a.m., just in time for the workday to begin.

The lunar eclipse will occur two days after an event called a “lunar perigee,” so the moon will appear noticeably larger; according to NASA, it will appear 5.3 times bigger than the last blood moon on April 15.

Tetrads are a relatively rare occurrence; we will only experience eight this century, with the next tetrad happening around 2032 or 2033. So bring your sleeping bags, pillows, and marshmallows- and all your best ghost stories for the campfire.